Self-cleaning substrates and methods for making the same

ABSTRACT

A methods, apparatus and compositions for producing colored, self-cleaning substrates by roll coating are provided. The roll coated, colored, self-cleaning substrates retain the predetermined color and a predetermined gloss of the colored coating, thereby facilitating their use in architectural applications. The roll coated, colored, self-cleaning substrates may be iridescent-free.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application claims priority to U.S. Provisional PatentApplication No. 61/230,953, filed Aug. 3, 2009, and entitled“SELF-CLEANING SUBSTRATES AND METHODS FOR MAKING THE SAME”, which isincorporated herein by reference in its entirety.

BACKGROUND

Titanium dioxide (TiO₂) may facilitate photocatalysis in the rightenvironmental conditions. However, applying coatings containing TiO₂ tosubstrates, such as for architectural products, without detrimentallyaffecting the aesthetic features of such substrates has proven difficultand cost ineffective.

SUMMARY OF THE DISCLOSURE

The present disclosure relates to methods of producing colored,self-cleaning substrates by roll coating. Roll coating, also known ascoil coating, is a high-speed process for applying coatings onsubstrates. These new colored, self-cleaning substrates retain theintend color and/or intended gloss of the initial substrate, therebymaking them suitable for architectural and other applications. Thecolored, self-cleaning substrate may also be iridescent-free.

“Roll coating”, sometimes called coil coating, and the like means anindustrial process for rapidly (e.g., at least 10 feet per minute, suchas in the range of 50-800 fpm) applying a coating to a substrate usingrolls which contact the surface of the substrate. Roll coating includesdirect roll coating, reverse roll coating and the like. Roll coatingusually involves the use of two or more of (i) a back-up roll, (ii) anapplication or coating roll, and (iii) a pick-up/metering roll, wherethe coating material is measured onto the applicator roller by aprecision setting of the gap between the metering roller and theapplication roller, as described in further detail below.

In one aspect, a method includes producing a colored sheet product(e.g., steel or aluminum) having a predetermined color by roll coatingthe sheet product. This roll coating step generally involves applying acolored coating to the sheet product. A colored coating is a coating(generally in the form of a liquid or colloid) that is adapted toproduce a colored layer having a predetermined color and/orpredetermined gloss. In one embodiment, a colored coating is acommercially available product, such as latex-based paints, oil-basedpaints, silicon-based coatings, and polymeric coatings, among others.

A predetermined color means a color that is picked in advanced, such asintended color of the end-use product. In some embodiments, thepredetermined color is different than that of the natural color of thesubstrate. In some embodiments, the predetermined color is achieved byapplication of a colored coating, such as a paint of a predeterminedcolor.

In some embodiments, the colored sheet product has a predeterminedgloss. A predetermined gloss is a gloss that is picked in advanced, suchas an intended gloss of the end-use product. In some embodiments, thepredetermined gloss is different than that of the natural gloss of thesubstrate. In some embodiments, the predetermined gloss is achieved byapplication of a colored coating, such as a paint of a predeterminedgloss.

In one embodiment, the sheet product is an aluminum alloy sheet product.An aluminum alloy sheet means an aluminum sheet or foil product producedfrom an aluminum alloy. An aluminum sheet product generally hasdimensions in the range of 0.006 inch to 0.249 inch (or sometimes up to0.5 or 0.75 inch). An aluminum foil product generally has dimensions ofless than 0.006 inch.

The producing a colored sheet product step may include converting thecolored coating into a colored layer, where the colored layer is locatedon an outer surface of the sheet product. In some embodiments, thecolored layer covers substantially all of a first side of the sheetproduct.

“Converting a colored coating into a colored layer” and the like meansto change the colored coating, which is generally in liquid form, into acolored layer, which is generally in solid form. The converting may beaccomplished, for example, via one or more of a change in temperature(e.g., due to radiation, convection, conduction) and/or time, which mayresult in evaporation of solvents and/or chemical reactions, to name afew. The converting may be accomplished concomitant to the applicationof a coating to the substrate.

“Colored layer” means a layer produced from a colored coating, and whichmay have a predetermined color and/or a predetermined gloss. Forexample, an aluminum alloy sheet material may have a colored layerhaving a predetermined color and/or a predetermined gloss, which may beuseful in architectural and other building applications, among others.In one embodiment, a colored layer includes organic constituents, whichmay degrade if exposed to photocatalytic processes. In one embodiment, acolored layer predominately includes carbon-based or polymeric-basedmaterials. In one embodiment, a colored layer is liquid impermeable(e.g., water impermeable) and may protect an underlying base (e.g., analuminum alloy sheet) from communication with liquid or other materialsthat may permeate and/or contact a surface of the base. In oneembodiment, the thickness of the colored layer is at least about 7microns. In other embodiments, the thickness of the colored layer is atleast about 10 microns, or at least about 20 microns. In one embodiment,the thickness of the colored layer is not greater than 150 microns. Inother embodiments, the thickness of the colored layer is not greaterthan about 100 microns, or not greater than about 75 microns, or notgreater than about 50 microns, or not greater than about 45 microns, ornot greater than about 40 microns. In one embodiment, the colored layerhas a thickness in the range of 20 to 37 microns.

Concomitant to the production of this first colored sheet product, orthereafter, an intermediate sheet product may be produced by rollcoating a barrier coating onto a at least a portion of the colored layerof the first colored sheet product to produce a barrier layer on atleast a portion of the colored layer. The roll coating process mayincluding applying a barrier coating to surfaces of the colored layerand converting the barrier coating into a barrier layer. After theconverting step, the barrier layer is located on at least a portion ofthe colored layer. In one embodiment, the barrier layer substantiallycovers the colored layer.

A barrier coating is a coating (generally in the form of a liquid orcolloid) adapted to produce a barrier layer. In one embodiment, abarrier coating is a silica containing coating, such as EASY CLEAN,produced by PPG Industries, Pittsburgh, Pa.

“Barrier layer” and the like means a layer configured to act as abarrier to a colored layer. In one embodiment, a barrier layer may actas a barrier between a colored layer and a self-cleaning layer, therebypreventing degradation of organic constituents of the colored layer. Inone embodiment, the barrier layer has a hydrophilicity that iscoincidental to that of a self-cleaning layer, and thus facilitatescoupling of the self-cleaning layer to the substrate. In one embodiment,a substrate having a barrier layer and/or a self-cleaning layer iscapable of passing the Scotch 610 tape pull test, as defined by ASTMD3359-02, Aug. 10, 2002. In one embodiment, the barrier layer has athickness of at least about 1000 Angstroms (0.1 microns). In otherembodiments, the barrier layer has a thickness of at least about 0.15micron, or at least about 0.2 micron. In one embodiment, the barrierlayer has a thickness of not greater than about 1 micron. In otherembodiments, the barrier layer has a thickness of not greater than about0.75 micron, or not greater than about 0.50 micron, or not greater thanabout 0.4 micron. In one embodiment, the barrier layer has a thicknessin the range of 0.2 to 0.3 micron.

“Converting a barrier coating into a barrier layer” and the like meansto change the barrier coating, which is generally in liquid form, into abarrier layer, which is generally in solid form. The converting may beaccomplished, for example, via one or more of a change in temperature(e.g., due to radiation, convection, conduction) and/or time, which mayresult in evaporation of solvents and/or chemical reactions, to name afew. The converting may be accomplished concomitant to the applicationof a coating to the substrate.

After this converting step, the intermediate sheet product retains thepredetermined color and/or retains the predetermined gloss of thecolored sheet product. This may be due to the use of silica basedbarrier coatings and/or due to the agitation of such barrier coatingsduring the application of the barrier coating to the sheet. The barrierlayer is generally transparent.

“Retains the predetermined color” means that the difference in colorbetween (i) the color of a substrate having only the colored layer and(ii) the color of a substrate having the colored layer and at least oneadditional layer (e.g., a barrier layer, a self-cleaning layer), is notgreater than about 10 Delta E. In some embodiments, the color differenceis not greater than about 9 Delta-E, or not greater than about 8Delta-E, or not greater than about 7 Delta-E, or not greater than about6 Delta-E, or not greater than about 5 Delta-E, or not greater thanabout 4 Delta-E, or not greater than about 3 Delta-E, or not greaterthan about 2 Delta-E, or not greater than about 1 Delta-E.

“Retains the predetermined gloss” means that the difference in glossbetween (i) the gloss of a substrate having only the colored layer and(ii) the gloss of a substrate having the colored layer and at least oneadditional layer (e.g., a barrier layer, a photocatalytic layer), is notgreater than about 20 units (e.g., % gloss units) as measured inaccordance with ASTM D 523. In some embodiments, the gloss difference isnot more than about 15 units or not more than about 13 units or not morethan about 10 units or not more than about 9 units or not more thanabout 8 units or not more than about 7 units or not more than about 6units or not more than about 5 units or not more than about 4 units ornot more than about 3 units or not more than about 2 units or not morethan about 1 unit. One instrument for measuring gloss is a BYK-GARDNERAG-4430 micro-TRI-gloss glossmeter.

Concomitant to the production of this intermediate colored sheetproduct, or thereafter, a self-cleaning sheet product may be produced byroll coating a self-cleaning coating onto a at least a portion of thebarrier layer of the intermediate colored sheet product to produce aself-cleaning layer on at least a portion of the barrier layer. The rollcoating process may including applying a self-cleaning coating tosurfaces of the barrier layer and converting the self-cleaning coatinginto a self-cleaning layer. After the converting step, the self-cleaninglayer is located on at least a portion of the barrier layer. In oneembodiment, the self-cleaning layer substantially covers the barrierlayer.

“Self-cleaning coating” means a coating (generally in the form of aliquid or colloid) that is adapted to produce a self-cleaning layer. Inone embodiment, the self-cleaning coating is a titanium dioxidecontaining coating (e.g., in the form of sol), such as the HYDROTECTproducts of TOTO (Tokyo, Japan) and/or the SAGAN products of the KONCorporation (Takeo-city, Japan). In some embodiments, the self-cleaningcoating is surfactant-free.

“Converting a self-cleaning coating into a self-cleaning layer” and thelike means to change the self-cleaning coating, which is generally inliquid form, into a self-cleaning layer, which is generally in solidform. The converting may be accomplished, for example, via one or moreof a change in temperature (e.g., due to radiation, convection,conduction) and/or time, which may result in evaporation of solventsand/or chemical reactions, to name a few. The converting may beaccomplished concomitant to the application of a coating to thesubstrate.

“Self-cleaning layer” and the like means a layer that has a high surfacetension surface and/or uses photocatalysis to facilitate cleaning of thesubstrate. In one embodiment, the self-cleaning layer is a titaniumdioxide layer. A titanium dioxide layer is a coating containing titaniumdioxide particles with particle sizes in the 10-50 nm range (generally).In one embodiment, a self-cleaning coating may actively break downmaterials that come in contact with its surfaces, such as dirt, grime,oil, dust, and/or mold, to name a few, (“visual detractants”) byutilizing sunlight, fluorescent light, blacklight or any other lightsource at wavelengths above about 300 nm, to photocatalytically breakdown the visual detractants. The visual detractants may then be removedfrom the surface via water (e.g., rain water). In other words, visualdetractants may decompose to simple organic or inorganic compounds,which re-enter the atmosphere and/or wash away under the effects ofambient conditions (e.g., heat, wind and/or rain), thus making the layerself-cleaning. Use of self-cleaning layers may provide an easier way tomaintain visually appealing surfaces, and an easier way to cleansubstrates, and in the absence of detergents, which may be harmful tothe environment, and in the absence of a dedicated water spray, whichmay waste water.

In one embodiment, the self-cleaning layer has a thickness of at leastabout 1000 Angstroms (0.1 microns). In other embodiments, theself-cleaning layer has a thickness of at least about 0.15 micron, or atleast about 0.2 micron. In one embodiment, the self-cleaning layer has athickness of not greater than about 1 micron. In other embodiments, theself-cleaning layer has a thickness of not greater than about 0.75micron, or not greater than about 0.50 micron, or not greater than about0.4 micron. In one embodiment, the self-cleaning layer has a thicknessin the range of 0.2 to 0.3 micron.

After this converting step, the self-cleaning sheet product retains thepredetermined color and/or retains the predetermined gloss of thecolored sheet product. This may be due to the use of self-cleaningcoatings containing little or no surfactants and/or the use ofsurfactants having low-foaming capabilities. The self-cleaning layer isgenerally transparent.

In one embodiment, the self-cleaning sheet product achieves a highwettability rating. A high wettability rating indicates that theself-cleaning layer of the product is substantially uniform across thewidth of the sheet product. In one embodiment, a substrate 1 containinga self-cleaning layer 30 achieves a uniformity rating of at least H, asmeasured in accordance with the below described wettability test. Inother embodiments, a substrate 1 containing a self-cleaning layer 30achieves a uniformity rating of at least G, or a uniformity rating of atleast F, or a uniformity rating of at least E, or a uniformity rating ofat least D, or a uniformity rating of at least C, or a uniformity ratingof at least B, or a uniformity rating of A.

These steps of roll coating the colored coating, the barrier coating andthe self-cleaning coating may be accomplished in series and via the useof a series of roll coating apparatus, and within a short period of timefrom one to the other. This embodiment may be useful for turning rawsheet product into a colored, self-cleaning sheet product at a singlelocation. In other embodiments, the colored sheet product is produced atone location, and then shipped to another location for application ofthe barrier coating and/or the self-cleaning coating.

Various ones of the above-described aspects, approaches and embodimentsmay be combined to produce various colored, self-cleaning substrates.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic, side-view of an embodiment of a portion of aself-cleaning substrate.

FIG. 2 is a schematic, side-view of an embodiment of a portion of aself-cleaning substrate.

FIG. 3 is a schematic, side-view of an embodiment of a portion of aself-cleaning substrate.

FIG. 4 is a schematic view of an embodiment of a roll coating system forproducing a self-cleaning substrate.

FIG. 5 is a schematic view of an embodiment of a roll coating system forproducing a self-cleaning substrate.

FIG. 6 is a flow chart illustrating various continuous methods ofproducing self-cleaning coatings.

FIG. 7 is a flow chart illustrating various batch methods of producingself-cleaning substrates.

FIG. 8 a is a photograph illustrating a self-cleaning substrate havingnon-uniform coatings, which are iridescence.

FIG. 8 b is a photograph illustrating a self-cleaning substrate havingnon-uniform coatings, which are iridescence.

FIG. 9 a is a graph illustrating the change in gloss from a coloredsubstrate to substrates having barrier layers and/or self-cleaninglayers.

FIG. 9 b is a graph illustrating the change in color from a coloredsubstrate to substrates having barrier layers and/or self-cleaninglayers.

FIG. 10 a is a photograph illustrating a self-cleaning substrate havinga uniform, substantially iridescent-free self-cleaning layer.

FIG. 10 b is a photograph illustrating a self-cleaning substrate havinga uniform, substantially iridescent-free self-cleaning layer.

FIG. 11 a is a chart illustrating test conditions for Example 3, sampleLRB 767.

FIG. 11 b is a chart illustrating test conditions for Example 3, sampleLRB 768.

FIG. 11 c is a chart illustrating test conditions for Example 3, sampleLRB 769.

FIG. 11 d is a chart illustrating test conditions for Example 3, sampleLRB 770.

FIG. 12 is a chart illustrating test conditions for Example 4, sampleLRB 776.

FIG. 13 is a chart illustrating the surface tension of various examplesubstrates.

DETAILED DESCRIPTION

Broadly, the present disclosure relates to substrates that realize acombination of one or more of: (i) self-cleaning properties, (ii) avisual appearance that meets consumer acceptance standards, and (iii) acost effective production methodology. In one embodiment, a substrateachieves at least two of these criteria. In one embodiment, a substrateachieves at least three of these criteria.

In one aspect, and with reference now to FIG. 1, a substrate 1 includesa base 10, an organic layer 20, and a self-cleaning coating layer 30.The base 10 may be an aluminum alloy base, as described in furtherdetail below. The organic layer 20 may be a painted layer, as describedin further detail below. The organic layer 20 may have a tailored colorand gloss, among others visual characteristics. The self-cleaningcoating layer 30 is a generally transparent layer that facilitatesself-cleaning while achieving a visual appearance that meets consumeracceptance standards. For example, the self-cleaning coating layer 30may facilitate retention of the gloss and color of the materialunderlying the self-cleaning coating layer, such as the organic layer20, while also being iridescent free.

Visual Appearance

In one embodiment, the self-cleaning coating layer 30 retains the glossof the material underlying the self-cleaning coating layer 30, such asthe gloss of the organic layer 20. For example, the gloss of thesubstrate may remain relatively unchanged after application of theself-cleaning coating layer 30. In one embodiment, the gloss of asubstrate having the self-cleaning coating layer 30 may change by notgreater than about 20 units (% gloss units) relative to the gloss of thematerial underlying the self-cleaning coating layer 30. In otherembodiments, the gloss of a substrate having a self-cleaning coatinglayer 30 changes by not more than about 15 units, or by not more thanabout 13 units, or by not more than about 10 units, or by not more thanabout 9 units, or by not more than about 8 units, or by not more thanabout 7 units, or by not more than about 6 units, or by not more thanabout 5 units, or by not more than about 4 units, or by not more thanabout 3 units, or by not more than about 2 units, or by not more thanabout 1 unit relative to the gloss of the material underlying theself-cleaning coating layer 30.

Gloss may be measured in accordance with ASTM D 523. One instrument formeasuring gloss is a BYK-GARDNER AG-4430 micro-TRI-gloss glossmeter,which is capable of measuring gloss as 20°, 60° and 85°. In oneembodiment, a glossmeter measures gloss at one of 20°, 60° and 85°, andthe substrate containing the self-cleaning coating layer 30 retains thegloss of the underlying material at this one angle. In one embodiment, aglossmeter measures gloss at two of 20°, 60° and 85°, and the substratecontaining the self-cleaning coating layer 30 retains the gloss of theunderlying material at these two angles. In one embodiment, a glossmetermeasures gloss at all three of 20°, 60° and 85°, and the substratecontaining the self-cleaning coating layer 30 retains the gloss of theunderlying material at all three angles.

In one embodiment, the self-cleaning coating layer 30 retains the colorof the material underlying the self-cleaning coating layer 30. Forexample, the color of the substrate may remain relatively unchangedafter application of the self-cleaning coating layer 30. In oneembodiment, the color of a substrate having a self-cleaning coatinglayer 30 may change by not greater than about 10 Delta-E relative to thecolor of the material underlying the self-cleaning coating layer 30. Inother embodiments, the color of a substrate may change by not greaterthan about 9 Delta-E, or not greater than about 8 Delta-E, or notgreater than about 7 Delta-E, or not greater than about 6 Delta-E, ornot greater than about 5 Delta-E, or not greater than about 4 Delta-E,or not greater than about 3 Delta-E, or not greater than about 2Delta-E, or not greater than about 1 Delta-E.

As known to those skilled in the art, Delta-E is a number thatrepresents the distance between two colors. Delta-E may be measuredusing LCH, LAB and other color parameters, and via a consistentillumination source (e.g., white light of a defined wavelength andwattage output) at a consistent, specified distance between the lightand the substrate, and via one of the various Delta-E equations. In oneembodiment, the Delta-E equation is based on dE76. In one embodiment,the Delta-E equation is based on dE94. In one embodiment, the Delta-Eequation is based on dE-CMC. In one embodiment, the Delta-E equation isbased on dE-CMC 2:1. In one embodiment, the Delta-E equation is based ondE2000. The parameters surrounding these Delta-E equations are known tothose skilled in the art, and are described, for example, in:

(1) “Historical development of CIE recommended color differenceequations”, by A. R. Robertson, Laboratory for Basic Standards NationalResearch Council of Canada Ottawa, Ontario, Canada K1A OR6, Paperpresented at the ISCC Conference on Color Discrimination Psychophysics,Williamsburg, Va., 1989, published in Color Research & Application, Vol.15, Issue 3, Pages 167-170, published online 2007 by Wiley Periodicals,Inc., A Wiley Company; and

(2) “The development of the CIE 2000 colour-difference formula:CIEDE2000”, by M. R. Luo et al. of the Colour & Imaging Institute,University of Derby, UK, in Color Research and Application, Vol. 26,Issue 5, pp. 340-350, published online 2001 by Wiley Periodicals, Inc.,A Wiley Company.

Each of these publications are incorporated herein by reference in theirentirety.

Delta-E may be measured using a consistent illumination source, locatedat a specified distance from the substrate, and a spectrophotometer(e.g., from Hunterlab, a.k.a., Hunter Associates Laboratory, Inc., 11491Sunset Hills Road, Reston, Va. 20190-5280). To determine the colordifference at two different viewing angles, the color values may bemeasured by the spectrophotometer at the first angle, and a secondangle, and Delta-E determined. The second angle is generally at least 15degrees different than the second angle, but is generally not more than165 degrees different than the first angle. In one embodiment, Delta-Eis measured in accordance with ASTM 2244. In one embodiment, Delta-E ismeasured using a Gretag Macbeth Coloreye 2246, or equivalentinstrumentation.

The self-cleaning coating layer 30 may be iridescent free. In oneembodiment, a substrate 1 containing a self-cleaning coating layer 30 isiridescent free, as determined via visual inspection. In one embodiment,the visual inspection is completed via the human eye, with a vision of20/20, and at an appropriate distance to detect iridescence in thesubstrate.

Uniformity, Thickness and Durability

To facilitate one or more of these visual appearance properties, theself-cleaning coating layer 30 may be relatively uniform. In oneembodiment, a substrate 1 containing a self-cleaning coating layer 30achieves a uniformity rating of at least H, as measured in accordancewith the below described wettability test. In other embodiments, asubstrate 1 containing a self-cleaning coating layer 30 achieves auniformity rating of at least G, or a uniformity rating of at least F,or a uniformity rating of at least E, or a uniformity rating of at leastD, or a uniformity rating of at least C, or a uniformity rating of atleast B, or a uniformity rating of A, as measured in accordance with thebelow described wettability test.

To facilitate one or more of these visual appearance properties, theself-cleaning coating layer 30 may be relatively thin. In oneembodiment, the self-cleaning coating layer 30 has a thickness of notgreater than about 1 micron. In other embodiment, the self-cleaningcoating layer 30 has a thickness of not greater than about 0.9, or notgreater than about 0.8 micron, or not greater than about 0.7 micron, ornot greater than about 0.6 micron, or not greater than about 0.5 micron,or not greater than about 0.4 micron, or not greater than about 0.3micron, or not greater than about 0.2 micron. The thickness of theself-cleaning coating layer 30 should be sufficiently large tofacilitate self-cleaning properties. In one embodiment, the thickness ofthe self-cleaning coating layer is at least about 0.05 microns.

The self-cleaning coating layer 30 may be durable. In one embodiment, asubstrate 1 containing a self-cleaning coating layer 30 isabrasion/scratch-resistant (e.g., as measured after normaldensification). In one embodiment, a substrate containing aself-cleaning coating layer 30 is able to consistently pass a pencilhardness test as defined by ASTM D3363-05. In these pencil hardnesstests, the substrate 1 may consistently pass/achieve a 5H or 6H rating,or higher. In one embodiment, the self-cleaning layer is adherent.Adherent to means that a surface is capable of passing the Scotch 610tape pull test, as defined by ASTM D3359-02, Aug. 10, 2002.

Self-Cleaning Properties Passive Self-Cleaning

The self-cleaning coating layer 30 facilitates self-cleaning properties.In one embodiment, the self-cleaning coating layer 30 is a passiveself-cleaning layer. A passive self-cleaning layer is one that does notutilize photocatalysis to facilitate cleaning of the substrate. Apassive self-cleaning layer generally is moderately hydrophilic andachieves a water contact angle of not greater than about 40°. In oneembodiment, a passive self-cleaning coating layer achieves a watercontact angle of not greater than about 37°. In other embodiments, apassive self-cleaning coating layer achieves a water contact angle ofnot greater than about 35°, or a water contact angle of not greater thanabout 30°, or a water contact angle of not greater than about 25°, or awater contact angle of not greater than about 20°, or a water contactangle of not greater than about 15°. Those skilled in the art canconvert these contact angle measurements to a surface tension value. Forexample, a contact angle below about 15 degrees equates to a surfacetension of ≧about 70 dyne/cm. For a contact angle of about 20 degreesthe surface tension is about 68 dyne/cm. For a contact angle of about 38degrees the surface tension is about 59 dyne/cm.

The passive self-cleaning coating layer may facilitate self-cleaningproperties via reduction of surface tension, as evidenced by the abovelow wetting contact angles. As a result, many contaminants (e.g.,organic contaminants) will not readily adhere to the surface of passiveself-cleaning coating layer. Furthermore, when water is applied (e.g.,via rain or washing), contaminants are readily removed via the water.

A passive self-cleaning coating later generally includes materials thatfacilitate the above-described visual appearance, uniformity, thickness,and/or durability properties while facilitating the reduction of surfacetension of the substrate. One passive self-cleaning coating layerincludes silica (SiO₂), such as when applied via an aqueous solutioncomprising silica. In one embodiment, the silica is applied via a rollcoating or a spraying process, as described in further detail below. Inone embodiment, a passive silica coating is achieved via application ofEASY CLEAN by PPG Industries, Pittsburgh, Pa.

Active Self-Cleaning

In one embodiment, the self-cleaning coating layer 30 is an activeself-cleaning layer. An active self-cleaning layer is one that utilizesphotocatalysis to facilitate cleaning of the substrate. An activeself-cleaning layer generally is very hydrophilic and achieves a watercontact angle of not greater than about 25°. In one embodiment, anactive self-cleaning coating layer achieves a water contact angle of notgreater than about 22°. In other embodiments, an active self-cleaningcoating layer achieves a water contact angle of not greater than about20°, or a water contact angle of not greater than about 18°, or a watercontact angle of not greater than about 15°, or a water contact angle ofnot greater than about 12°, or a water contact angle of not greater thanabout 10°, or a water contact angle of not greater than about 8°, or awater contact angle of not greater than about 7°.

Like the passive self-cleaning coating layer, an active self-cleaningcoating layer may facilitate self-cleaning properties via reduction ofsurface tension, as evidenced by the above low wetting contact angles.As a result, many contaminants (e.g., organic contaminants) will notreadily adhere to the surface of passive self-cleaning coating layer.Furthermore, when water is applied (e.g., via rain or washing),contaminants are readily removed with the water.

Additionally, an active self-cleaning coating layer may facilitatecleaning via photocatalysis. In this embodiment, the self-cleaningsubstrates may actively break down materials that come in contact withsurfaces of the substrate, such as dirt, grime, oil, dust, and/or mold,to name a few, (“visual detractants”) by utilizing sunlight, fluorescentlight, blacklight or any other light source at wavelengths above about300 nm, to photocatalytically break down the visual detractants. Thevisual detractants may then be removed from the surface via water (e.g.,rain water). In other words, visual detractants may decompose to simpleorganic or inorganic compounds, which re-enter the atmosphere and/orwash away under the effects of ambient conditions (e.g., heat, windand/or rain), thus making the substrates self-cleaning. Use ofself-cleaning substrates provides an easier way to maintain visuallyappealing surfaces, and an easier way to clean substrates, and in theabsence of detergents, which may be harmful to the environment, and inthe absence of a dedicated water spray, which may waste water.

Photocatalysis means the use of light to excite a catalyst on a surfaceto release energy. The catalyst is not consumed by this reaction. Theenergy released from the catalyst is used to start a reaction, orreaction sequence. Semiconductors can have photocatalytic properties.

Semiconductors are any of various solid crystalline substances, such asgermanium, titanium, indium or silicon, or the oxides of thesecrystalline substances, having electrical conductivity greater thaninsulators. Semiconductors are distinguished from insulators by a bandgap energy. Band gap energy is the energy that electrons must have tomove from a valence band to a conduction band. There is an arbitraryband energy assigned of 4.0 electron volts (ev) to separatesemiconductors from insulators. Semiconductors have a band gap of lessthan or equal to 4.0 electron volts. Titanium dioxide in the anatasecrystalline form has a band gap of 3.2 ev.

In one embodiment, the active self-cleaning coating layer is a titaniumdioxide layer. A titanium dioxide layer is a coating containing titaniumdioxide particles with particle sizes in the 10-50 nm range (generally).The coating may also contain clay, mineral, alkali and/or othersemiconductor(s).

The photocatalytically active self-cleaning coating layer may include aplurality of a photocatalytically active semiconductor fine particles.The particles may be uniformly dispersed within the layer (sometimesreferred to herein as film) or may be non-uniformly dispersed in thefilm. The particles are located in the film so that at least a portionof the fine particles are partially exposed to the environment throughthe surface of the film so as to facilitate self-cleaning functionality.In one embodiment, titanium dioxide is used as the photocatalyticallyactive semiconductor. Suitable types of photocatalytically active TiO₂semiconductors that may be used include, but are not limited to,anatase, rutile and brookite crystalline forms of titanium dioxide andor combinations thereof. In one embodiment, the photocatalyticallyactive film is an anatase titanium dioxide layer, where the titaniumdioxide particles are in a size range of about 10 to about 50 nm. In oneembodiment, the photocatalytically active film is produced from TOTOTHPC090402WC-A, which is an aqueous based liquid containing about 0.5-10wt. % silica, 85-95 wt. % water, and 0.2-5 wt. % titanium dioxide. Inthis embodiment, TiO2 is the active material and silica is the filmformer. In one embodiment, a surfactant, such as an organic liquid(e.g.,poly(oxy-1,2-ethanediyl),alphamethylomega-[3-[1,3,3,3-tetramethyl-1-[(trimethylsilyl)oxy]-1-disiloxanyl]propoxy]-)is used with the aqueous based liquid.

It is believed that the mechanism of the photocatalytically activesemiconductor works as follows: once the photocatalytically activesemiconductor, for example TiO₂, is illuminated by ultraviolet lightwith a wavelength above about 300 nm, electrons in the valence band areexcited to the conduction band. When the electrons return to their lowerenergy state, energy is emitted and interacts with water vapor or oxygenmolecules to form hydroxyl radicals and super oxide anions,respectively. Both the hydroxyl radicals and superoxide anions arestrong oxidizing species, which can react and breakdown organicpollutants into simpler, lower molecular weight, oxidized products.

Barrier Layer

In one embodiment, and with reference now to FIG. 2, a self-cleaningcoating layer 40 may be coupled to a second layer (e.g., non-organic),or a barrier layer. For example, an active self-cleaning coating layer40 may detrimentally interact with an organic layer 20, such as paintedlayer, due to, for example, the catalytic properties of the activeself-cleaning coating layer. In these instances, a barrier layer 30 maybe used, which may act as a barrier between the organic layer 20 and theactive self-coating cleaning layer 40. In the illustrated embodiment,the barrier layer 30 is a passive self-cleaning coating layer 30 (e.g.,a coating containing silica). In this embodiment, the combination ofthese two layers 30, 40 may still achieve the above-described visualappearance, uniformity, thickness, and/or durability properties whilefacilitating the reduction of surface tension and/or active selfcleaning properties of the substrate. In these embodiments, the barrierlayer 30 should be sufficiently thick so as to facilitate adhesion ofthe self-cleaning coating layer 40 to the barrier layer, but should besufficiently thin to still achieve the above-described visual appearancestandards. For example, the barrier layer 30 may have similar thicknessand uniformity to those described above with respect to theself-cleaning layer of FIG. 1. Likewise, the self-cleaning coating layer40 should be sufficiently thick so as to (i) facilitate adhesion to thebarrier layer 30, (ii) durability of the substrate 1, and, in someinstances, (iii) sufficient surface area and mass transport capabilitiesto facilitate photocatalysis, but should be sufficiently thin to stillachieve the above-described visual appearance standards. For example,the self-cleaning coating layer 40 may have similar thickness anduniformity to those described above with respect to the self-cleaninglayer of FIG. 1

Coupled to means joined to another surface. For example, aphotocatalytically active film or layer may be at least partiallycoupled to a barrier layer via the physical interaction between thematerials of those two layers. In one embodiment, a first material maybe coupled to a second material, and the first material may also beadherent to the second material. Adherent to means that a surface iscapable of passing the Scotch 610 tape pull test, as defined by ASTMD3359-02, Aug. 10, 2002.

CO₂ Removal

In one embodiment, a self-cleaning coating layer 40 is configured toalso remove carbon dioxide from surrounding gases. Methods forconfiguring coatings (e.g., coatings containing photocatalyticallyactive substances) to remove carbon dioxide, and systems andcompositions relating to the same, are described in commonly-owned U.S.patent application Ser. No. 11/828,305, entitled “SURFACES AND COATINGSFOR THE REMOVAL OF CARBON DIOXIDE”, filed Jul. 25, 2007, which isincorporated herein by reference in its entirety.

Base Material

The base material 10 may be any material that can have self-cleaningcoatings. In one embodiment, the base material 10 is aluminum or analuminum alloy, such as any of the aluminum association series 1xxx,2xxx, 3xxx, 4xxx, 5xxx, 6xxx, 7xxx, 8xxx or 9xxx aluminum alloys. Asdescribed below, aluminum-containing base materials 10 having an organiclayer 20 are particularly difficult to produce via high production ratesystems (e.g., via roll coating) due to the thermal limitations imposedon the processing of aluminum and/or the organic material coupledthereto. The base material 10 may be a wrought aluminum product or acast aluminum product. In one embodiment, the wrought aluminum productis a sheet, foil or plate product. In one embodiment, the rolled producthas a thickness of at least about 0.1 mm. In one embodiment, the wroughtaluminum product is an extrusion. In one embodiment, the wroughtaluminum product is a forging. In one embodiment, the base material 10is an aluminum alloy suited for use in any of the commercialapplications noted below. In one embodiment, the base material 10 isbrushed aluminum. In one embodiment, the base material 10 is a compositealuminum product, such as a laminate aluminum product, including thosedescribed in commonly-owned U.S. Pat. No. 6,455,148.

Other base materials, such as other metals (e.g., steel, titanium) maybe used. Non-metallic materials may also be employed as the base 10. Forexample, plastics, glass, composites, fibers, ceramics, cements,laminates, particulates, meshes, sieves, aerogels, papers, andcombinations thereof, to name a few, may be utilized as the base 10. Inone approach, the base 10 may comprise mixtures of metals andnon-metallic materials. For example, the base 10 may comprise metalsheets sandwiching a polymeric sheet therebetween. Conversely, the base10 may comprise non-metallic materials sandwiching a metal materialtherebetween. Various other combinations exist to produce the base 10.

Organic Layer

The substrate 1 may include an organic layer 20 coupled to the base 10.An organic layer means a layer comprising predominately carbon-based orpolymeric-based materials. In one embodiment, the organic layer 20 isliquid (e.g., water) impermeable and may protect the underlying base 10from communication with liquid water or other materials that maypermeate and/or contact a surface of the base 10. In one embodiment, theorganic layer 20 comprises materials produced from commerciallyavailable products, such as latex-based paints, oil-based paints,silicon-based coatings, polymeric coatings, and others. In oneembodiment, the organic layer 20 comprises a predetermined pigmentand/or sheen so as to provide the body 10 with the desired color and/orgloss features.

Base-to-Self-Cleaning Layer

In one embodiment, and as illustrated in FIG. 3, a substrate 1 includesa self-cleaning coating directly in contact with the base material 10.For example, a base 10 comprising an aluminum alloy may be directlycoupled to either a passive self-cleaning layer 30 or an activeself-cleaning layer 40.

Methods and Systems for Producing Self-Cleaning Substrates

To produce the self-cleaning substrates at commercially viableproduction rates, roll coating or spraying may be employed. Oneembodiment of a method and system for producing self-cleaning substratesvia roll coating is illustrated in FIG. 4. In the illustratedembodiment, the roll coating system 500 coats a substrate 1 (e.g., ametal strip) via a back-up roll 510, an application or coating roll 520,and a pick-up/metering roll 530.

Liquid coatings are applied to substrates in a variety of methodsincluding spray, dip, roll, knife, electrodeposition, vapor deposition,slot, and curtain coating. For metallic substrates (e.g., aluminum),liquid coating is commonly transported to the applicator roll via directcontact with a bath, by contact with a second roll that has contact witha bath, by direct spraying onto the roll, and the like. The rolls canhave a metal, plastic or other type surface depending on the material tobe coated. The various rolls in a roll coater are usually given commonnames associated with their function. In the four roll configurationshown in FIG. 5, the applicator roll 520 applies the coating to the web1, and the backup, or impression roll 510 provides support for the web.If the roll 510 is deformable (rubber-covered) it is an impression rollwhile a non-deformable roll 510 is a backup roll. Thepickup/metering/fountain roll 530 lifts coating from the pan and meterscoating with applicator roll 520. Since roll 530 has two functions, itcan be called by more than one name. Depending on the number of rolls inthe configuration, additional terms such as transfer roll and spreadingroll are commonly used to describe the roll function in a specificindustry. The narrow gap between roll 520 and roll 530 is termed themetering nip and the narrow gap between roll 530 and the web 1 is termedthe coating nip. The back-up roll 510 supports the web 1 at the point ofcoating application. If space is maintained between the applicator roll520 and the web 1, the back-up roll 510 is usually rigid, and there isno metal-to-metal contact. If the backup roll 510 is forced intonear-contact with the 520 applicator roll, one of the two rolls isgenerally covered with deformable material to prevent metal to metalcontact. Surfaces that move in the same direction at the point ofnearest contact (rolls 520 and 530) are said to be moving in a forwarddirection, and those in opposite direction (roll 510 and the web 1) in areverse direction. For the most uniform surface appearance, theapplicator roll 520 moves in a reverse direction for continuous webcoating. A description of various roll combinations and descriptions offluid dynamics can be found in Liquid Film Coating, Ed. S. F. Kistler etal. “Knife and Roll Coating” by Dennis J. Coyle, pp 539-542 (1997).

In the area of coating metallic substrates for packaging andarchitectural end uses, metallic substrates are coated in one of twoways: as a continuous web or as approx. one m² (10 ft²) sheets. Acontinuous “web” is rewound into a coil for subsequent trimming,slitting, or fabrication. Aluminum and steel are most commonly used asthe substrate. Many coatings are applied on metal webs via forward orreverse roll coat with a deformable applicator roll 520.

For applying the self-cleaning coatings of the present disclosure, theapplicator roll 520 generally has a pliable covering about 5-50 mm thickmade from urethane, EPDM rubber or similar pliable material. Thecovering Shore A hardness, referred to as durometer, is about 45-85(e.g., about 65), and the surface roughness R_(a) is about 20-80 microinches. R_(a) is determined by first finding a mean line parallel to thegeneral surface direction, dividing the surface such that the sum of theareas formed above the line is equal to the sum of the areas formedbelow the line, and computing the surface roughness summing the absolutevalues of all the areas above and below the mean line and dividing bythe sampling length. This allows the applicator roll 520 to transferliquid coating to the web 1 and conform to any web surfaceirregularities or roll irregularities to ensure complete coverage at auniform film thickness.

In one embodiment, a continuously fed and moving fairly thick metalsubstrate sheet 1 passes over a pass, which can bend to roller pressurebut is considered “non-deformable”, in contrast to thin metal foil,paper, and the like line roll 528 to directly contact the applicatorroll 520. Substrate thickness for a continuous process of this inventionwill generally be between about 0.1 mm to 0.8 mm, such as between about0.100 mm to 0.500 mm. The coating rate will vary widely depending on thecoating liquid viscosity and coating thickness desired, but will usuallybe from about 5 m/min to 500 m/min, such as from about 200 in/min to 400m/min.

A source of self-cleaning coating precursor liquid 514 is provided andis usually held in an appropriate type container 526, although thecoating liquid may, in some instances, be sprayed on an applicator roll.The precursor liquid 514 is generally aqueous and contains particulatematter, such as TiO2 or SiO₂. The particulate size is generally in therange of 0.01 micron to about 0.2 to 0.3 micron. The precursor liquid isgenerally has a viscosity of about 1 centipoise (where one-thousandcentipoises (cP) equals one Pascal-second). These precursor liquids,once applied, can be air-dried, UV (ultraviolet) or EB (electron beam)cured, heat cured, or the like, to provide the desired resulting “cured”coating. In one embodiment, the precursor liquid may contain a suitablesurfactant to facilitate wetting of the substrate 1 surface, such aswhen an organic layer 20 is included. Preferred surfactants includethose that are non-foaming. In one embodiment, the precursor liquidresults in a passive self-cleaning coating, such as EASY CLEAN producedby PPG of Pittsburgh, Pa. In one embodiment, the precursor liquidresults in for an active self-cleaning coating, such as THPC090402WC-A(Waterborne Photocatalyst Clear Coating-A) by TOTO, Japan, or TPX-220 TSor TPX-85 TS by Kon Corporation, Japan.

The container 526 may include an agitator (not illustrated), such as astir rod, to facilitate even application of the precursor liquid andattainment of a suitable visual appearance. In one embodiment, theprecursor liquid is continuously or near continuously agitated so as tofacilitate mixing and production of iridescent-free coating surfaces. Ithas been found that coatings applied in the absence of agitation may notrealize an iridescent-free appearance. In one embodiment, an air driven,slow speed agitator is used inside the coating reservoir in conjunctionwith a pumping system that uses cross coating pan flow. In other wordsthe coating exits the pump and enters the left side of the coating pan.The coating exits the pan, and moves back to the coating reservoir onthe right side of the coating pan.

The applicator roll 520 may reverse roll coat (rolls opposite tosubstrate) the moving substrate 1, as shown in FIG. 4 since the wet filmthickness is more uniform than with forward roll coating due to thelocation of the film split meniscus. Forward roll coating with theapplicator roll 520 is possible providing the coating hydrodynamicforces keep the surfaces separate. It is believed that the smoothness ofthe applicator roll 520 may facilitate maintenance of a stable coatingbead/meniscus at high line speeds. As the applicator rolls turns faster,the tendency to drag air into the bead can disrupt the bead and cause acoating perturbation, or simply ‘whip’ air into the heretoforebubble-free liquid. The applicator roll generally will apply a pressureon the substrate 1 of from about 0.3 kg/cm² to 3.0 kg/cm₂ (4 psi to 40psi).

The applicator roll 520 can be located/disposed directly opposite themetering roll 530 and a backup roll 510 as shown in the embodiment ofFIG. 4, where for example only one side of the substrate is to becoated. The backup roll 510 supports the moving substrate 1. Asmentioned previously, it is advantageous to locate the applicator roll520 in close proximity, but not to permit actual contact with the backuproll 510, for both safety reasons and coating weight variations fromroll out of roundness. It is helpful to arrange the rolls such that awrap angle of about 2 to 10 degrees is maintained to ensure a stablecoating process. Wrap angle is the portion of the roll circumferencethat is covered by the web, expressed in degrees. FIG. 4 shows a reverseroll coat configuration, and this is one of many possible configurationsfor roll coating substrates 1. For best coating appearance anduniformity, the applicator roll 520 moves in the opposite direction sothat the web realizes a smoother coating. Depending on coating flowafter application and quality standards, forward roll coating is may bepractical. An additional top guide roll 527 may be used as is also shownin FIG. 4.

FIG. 5 illustrates a coating configuration where both sides of themetallic web are reverse roll coated under sheet tension, where in thatembodiment, both sides of the moving substrate are coated with the sameor different coating liquids 514 and 514, using two separate meteringrolls 530 and two separate applicator rolls 520, where each applicatorroll 520 is spaced apart from dual backup rolls 510. As shown, themetering rolls 530 and applicator rolls 520 move in opposing directionssimilarly to FIG. 4. In FIG. 5, the applicator rolls 520 move in theopposite direction as the moving substrate 1 which initially passes overoptional turn roll 528. As shown, the initial (first to coat) applicatorroll is disposed between at least two, here dual idler rolls 510.

In either instance, the distance between the applicator roll 520 and themetering roll 530 should be sufficiently short so as to facilitate atight metering nip. A tight metering nip facilitates production of thin,uniform self-cleaning coating layers.

The precursor liquid 14 is preferably contacted with/applied to ametering roll 530 to coat the metering roll 530. This metering roll 530is the roll to which liquid coating is initially applied and can be ofany type effective to carry the coating liquid to the applicator roll520. The metering roll 530 can be porous or non-porous, but generallyhas a surface roughness sufficiently high to enable metering ofsufficient precursor liquid to the applicator roll 520. In this regardthe metering roll 530 may be nickel or chrome-steel plated, having asurface roughness (R_(a)) of about 150. The liquid 514 is held in anappropriate container 526 as shown in FIG. 5 and the metering roll movesin the forward direction with applicator roll 520, to facilitate smoothpick-up of precursor liquid 514.

The roll coating may produce material at a rate of at least about 10feet per minute (fpm). In one embodiment, the roll coating producesmaterial at a rate of at least about 25 fpm. In other embodiments, theroll coating produces material at a rate of at least about 50 fpm, or atleast about 75 fpm, or at least about 125 fpm, or at least about fpm. Inone embodiment, the roll coating may produce material at a rate of notgreater than about 800 fpm. In other embodiments, the roll coatingproduces material at a rate of not greater than about 700 fpm, or notgreater than about 600 fpm. In some instances, the pick-up roll andmetering roll are the same roll. In other instances, the pick-up roll isseparate from the metering roll.

When roll coating multiple coatings, such as organic coating, a barrierlayer, and an active self-cleaning layer in series, the roll coatingsystem can be arranged to have a series of rolls, ovens and/or coolersfor each coating to facilitate the serial production of substrateshaving multiple coatings.

Below are some embodiments of metering-to-applicator rollconfigurations, for reverse roll coat and forward roll coatconfiguration, as appropriate:

Config- uration Metering Roll Applicator Roll 1 Smooth/rough Hardmetering Smooth/rough soft roll (chrome, steel, (urethane/rubber/other)ceramic finish or other) coated applicator roll 2 Smooth/rough Hardmetering Smooth/rough hard applicator roll (chrome, steel, roll (chrome,steel or ceramic finish or other) ceramic finish, other) 3 Smooth/roughHard metering Smooth/rough soft roll (chrome, steel,(urethane/rubber/other) ceramic finish or other) coated applicator roll

Methods of producing various self-cleaning substrates are alsoillustrated in FIGS. 6 and 7. With respect to FIG. 6, a first sheetproduct may be produced by roll coating (coil aluminum alloy sheet).This first sheet product may include an organic layer, such as paint. Abarrier coating is then roll coated onto the first sheet product (coilcoat PPG easy clean coating; coil coat other inorganic barrier coatingwith refractive index similar to silica). The process may end here, inwhich a hydrophilic coil coated sheet product is produced (Easy CleanSheet). Alternatively, a self-cleaning coating may then be roll coatedonto this intermediate product (coil coat photocatalytic coating). Theprocess may end here, in which an active self-cleaning, superhydrophobicsheet product is produced (photocatalytically active sheet).Alternatively, the sheet product may be laminated with another productto form an aluminum composite material. This may be with only thebarrier coating (hydrophilic aluminum composite materials; easy cleanACM) or with the barrier coating and the self-cleaning coating (activeself-cleaning, superhydrophobic aluminum composite material;photocatalytically active ACM). As illustrated in FIG. 7, similarproducts could be achieved with batch spray processes.

Commercial Applications

The self-cleaning substrates disclosed herein may be used in a varietyof commercial applications due to their low-cost production methodology.For example, the substrates could be used as an architectural product,including building exterior wall panels, including aluminum compositematerials (ACM), foam panel, rib panels, soffit, and flashing, to name afew. Post-painted products and other factory manufactured buildingmaterials, such as roofing, vinyl siding, terracotta, and brick, may bea useful substrate for coating with a self-cleaning coating. Othersubstrates include materials used in metal signage, airplanes,automobiles (e.g., cars, trucks, trailers), highway sound barriers andguards, and industrial manufacturing venting systems, to name a few.Materials for interior programs may also benefit from self-cleaninglayers, such as metal, laminate, hardware, plastic, paper based ceilingpanels, doors, furniture, duct work for commercial buildings, and othernon-wear surfaces. The substrate may also be a food container, such asan aluminum can, where, just before filling the can with a food orconsumable liquid, a UV light may be used to clean the wall ofpathogens, thereby extending shelf life and increasing product safety.The self-cleaning substrate may also be useful electronic devices, solardevices, wind powered devices, environmental sensors, battery technologyand polymer electronics.

Various ones of the unique aspects noted hereinabove may be combined toyield visually appealing, self-cleaning substrates at commerciallyviable production rates. These and other aspects, advantages, and novelfeatures of the disclosure are set forth in part in the description thatfollows and will become apparent to those skilled in the art uponexamination of the following description and figures, or may be learnedby practicing the disclosure.

Wettability Test

I. Materials and Apparatus

1. Squeeze type polyethylene bottle for each solution.

2. Solutions:

-   -   A—100% Distilled Water    -   B—90% Distilled Water, 10% Denatured Ethyl Alcohol    -   C—80% Distilled Water, 20% Denatured Ethyl Alcohol    -   D—70% Distilled Water, 30% Denatured Ethyl Alcohol    -   E—60% Distilled Water, 40% Denatured Ethyl Alcohol    -   F—50% Distilled Water, 50% Denatured Ethyl Alcohol    -   G—40% Distilled Water, 60% Denatured Ethyl Alcohol    -   H—30% Distilled Water, 70% Denatured Ethyl Alcohol

II. Procedure and Evaluation

1. Inclined coated substrate approximately 45° to the horizontal.2. An “A” solution is applied across the entire width of the web fromthe polyethylene applicator using a rapid sweeping motion.3. If the sheet is “A” wettable, the top edge of the stream will notdepart from its straight line before 5 seconds after application.4. If the stream pulls from its initial straight line before 5 seconds,the “B” solution is then tried on a fresh wrap of sheet. If a “B”solution fails to wet the surface, a “C” solution is tried and so on.5. The solution which wets the entire web is the wettability rating.

EXAMPLES Example 1 Spray Coating

An aluminum alloy substrate is spray coated with PPG Easy Coat, andcured. The coating is iridescent. Photos of the iridescent coating areillustrated in FIGS. 8 a-8 b.

Example 2 Brush Rolled Substrates

Three cream-colored painted aluminum alloy substrates are produced. Afirst substrate is used as a control. A second substrate is coated withPPG Easy Clean via a roll brush and cured (passive coating). A secondsubstrate is coated with PPG Easy Clean via a roll brush and cured(passive coating), and is then coated with TOTOTHPC090402WC-A+THPC090402WC-B via a roll brush and cured. Color andgloss change is tested via the three substrates by exposure to a QUV Abulb for a period of 1000 hours. As illustrated in FIGS. 9 a-9 b, thegloss of the underlying color is only slightly decreased, while thecolor change difference is negligible, both for single layerself-cleaning coatings, and dual-layer self-cleaning coatings.

Example 3 Roll Coating—Urethane Roll

Various painted aluminum alloy substrates are roll coated via a pilotcoil roll coating line. The system used to roll coat is similar to thatillustrated in FIG. 5. A barrier coating is applied to a coloredaluminum sheet product having a predetermined color and gloss. Thebarrier coating is converted to a barrier layer. A self-cleaning coatingis then applied to the barrier layer, and is then converted to aself-cleaning layer. The roll coating conditions and wettability resultsare provided in further detail below. The produced colored,self-cleaning substrates retain the predetermined color and gloss of thealuminum alloy sheet product. The colored, self-cleaning substrates areiridescent-free as illustrated in FIGS. 10 a-10 b. The colored,self-cleaning substrates have uniform self-cleaning layers asillustrated in FIGS. 10 a-10 b. In other words, the aluminum alloysubstrates achieve an iridescent-free surface while retaining the colorand gloss of the underlying paint. These uniform and visually appealingsurfaces are generally achieved when there is a tight nip between theapplicator roll and the metering roll.

Conditions for Example 3 Tests

Overview: The purpose of this trial is to determine if the self cleaningcoating systems could be applied by a reverse roll coat coil operation.Small coils (300 linear feet) are produced for field testing. All fourcoatings applied well. Line trials confirmed that the rough chrome roll(150 Ra) assisted in successful roll coat application. Each coatingimproved the surface tension of the incoming substrate as determined bycontact angle measurement. Surface energy went from around 45 dynes/cmto at least about 68 dynes/cm, as illustrated in FIG. 13. Curingtemperature and time had little impact on the coatings appearance orsurface energy change. Curing variations tested were: high oventemperature at a long dwell time (about 650° F. for about 11 seconds,PMT of about 410° F.) and low oven temperature at a short dwell time(about 250° F. for about 5.5 seconds, PMT of less than about 210° F.).Ten (10) small coils were produced for testing.

Line Conditions/Run Details

-   -   Line Speed of 150 FPM (11.2 second oven dwell time)        -   i. Applicator roll at 50% over line speed        -   ii. Pick-up roll at 40% under line speed    -   Both oven zones set 250° F.        -   i. High velocity temperature: Varied—See FIGS. 11 a-11 d        -   ii. Low velocity temperature: Varied—See FIGS. 11 a-11 d    -   Coatings:        -   i. LRB 767—PPG UC108219 (barrier)        -   ii. LRB 768—Toto THPC090402WC—water base (self-cleaning)        -   iii. LRB 769—Kon TPX 220TS (self-cleaning)        -   iv. LRB 770—Toto TPCA001 solvent base    -   Reducing Solvent: None for all coatings    -   Application Viscosity: No adjustment required; run as received,        water thin at about 71° F.    -   Roll Types:        -   i. Top side applicator=urethane 65 durometer, 11.0 inch            diameter        -   ii. Top side pickup roll chrome plated, 150 Ra, 6.0 inch            diameter        -   iii. Bottom side applicator, urethane 55 durometer, 6.0 inch            diameter        -   iv. Bottom side pickup roll chrome plated, 150 Ra, 6.0 inch            diameter    -   Roll Direction:        -   i. Reverse roll coated, top & bottom side coated against            sheet tension    -   Roll Speeds: Various—See FIGS. 11 a-11 b    -   Substrate:        -   i. LRB 767 trials 1-7 AAP's polyester white coated surface,            0.035″        -   ii. LRB 767 trials 8-11 AAP's kynar white coated surface,            0.020″        -   iii. LRB 768 trials 1-4 ATC's LRB 767 T-3        -   iv. LRB 768 trials 5-6 ATC's LRB 767 T-10        -   v. LRB 769 trials 1-3 ATC's LRB 767 T-3        -   vi. LRB 769 trial 4 ATC's LRB 767 T-9        -   vii. LRB 770 trials 1-4 ATC's LRB 767-9        -   viii. LRB 770 trials 5-7 ATC's LRB 767 T-2    -   Resulting products (300 linear foot coils of each of the        following):        -   i. LRB767-1 PPG Ez Clean UC108219 over polyester white        -   ii. LRB767-2 PPG Ez Clean UC108219 over polyester white        -   iii. LRB767-3 PPG Ez Clean UC108219 over polyester white        -   iv. LRB767-4 PPG Ez Clean UC 108219 over polyester white        -   v. LRB767-5 PPG Ez Clean UC108219 over polyester white        -   vi. LRB767-8 PPG Ez Clean UC108219 over kynar white        -   vii. LRB767-9 PPG Ez Clean UC108219 over kynar white        -   viii. LRB767-10 PPG Ez Clean UC108219 over kynar white        -   ix. LRB 768-4 PPG UC108219+Toto THPC090402WC over polyester            white        -   x. LRB 768-5 PPG UC108219+Toto THPC090402WC over kynar white        -   xi. LRB 769-3 PPG UC108219+Kon 90603 over polyester white        -   xii. LRB 769-4 PPG UC108219+Kon 90603 over kynar white        -   xiii. LRB 770-4 PPG UC108219+Toto TPCA001 over kynar white

Product Observations:

-   -   LRB 767 sample:        -   i. PPG Ez-Clean, UC108219 (Trials 1-11)            -   1. Good coating flow (slight crows feet appearance)            -   2. Coating viscosity was stable in the pan            -   3. Coating was easy to clean up with water followed by a                MEK wipe            -   4. Uniform gloss            -   5. Appearance better over matte finish            -   6. Wipes off directly after curing (allow longer time to                cure)    -   LRB 768 sample:        -   i. Toto THPC090402WC-A (Trials 1-6)            -   1. Good coating flow (slight crows feet appearance)            -   2. Coating viscosity was stable in the pan            -   3. Coating was easy to clean up with water followed by a                MEK wipe            -   4. Uniform gloss            -   5. Two component mixture            -   6. Severe foaming in pump bucket            -   7. Appearance better over matte finish            -   8. Wipes off directly after curing    -   LRB 769 sample:        -   i. KON TPX-220TS (Trials 1-4)            -   1. Good coating flow (slight crows feet appearance)            -   2. Coating viscosity was stable in the pan            -   3. Coating was easy to clean up with water followed by a                MEK wipe            -   4. Uniform gloss            -   5. Appearance better over matte finish            -   6. Wipes off directly after curing    -   LRB 770 sample:        -   i. TOTO TPCA001 (Trials 1-7)            -   1. Good coating flow            -   2. Coating viscosity was stable in the pan            -   3. Coating was easy to clean up with MEK            -   4. Uniform gloss            -   5. Appearance better over matte finish            -   6. Wipes off directly after curing

Example 4 Roll Coating

Various painted aluminum alloy substrates are roll coated via a pilotcoil roll coating line. The system used to roll coat is similar to thatillustrated in FIG. 5, except that the applicator roll is hard roll. Theroll coating conditions are provided in detail below. It is difficult toachieve iridescent-free surfaces—the hard-to-hard rolling does notfacilitate uniform and thin application of the precursor liquids. Aurethane roll was then used, resulting in good uniformity and thickness.After application of a barrier coating (PPG Easy Clean), a self-cleaningcoating (TOTO) is applied to the substrate via roll coating. The TOTOcoating is applied without surfactant and is adherent to the surface ofthe barrier layer.

Conditions for Example 4 Test

Overview: The purpose of this trial is to:

-   -   Determine whether self cleaning coatings could be applied by a        reverse roll coat coil operation containing two hard rolls;    -   determine whether the surfactant portion of the self-cleaning        coating (TOTO part B) of the two component system (TOTO        HydroTect) was necessary to wet the pre-coated substrate. The        substrate was previously coated with PPG's UC108219 coating; and    -   Modify the pumping equipment to minimize foam build while using        this two component coating system.        Line trials utilizing the two hard rolls has mixed results. The        coating are successfully applied, but there is no control of        coating film thickness. This application method produces sheet        with areas of non-uniform layers. Roll roundness appears to be        the issue; without a deformable roll the unevenness is difficult        to remove. While in the two hard roll configuration, the rough        pick-up roll is worn smooth after several hours of operation.        Adding the surfactant to the self-cleaning coating did not        appear to correct the uneven thickness issue. This suggested        that surfactant is not necessary when applying it to a barrier        layer made from PPG's UC108219 EZ-Clean barrier coating.        Extension of the pumping system return pipe reduced foam build        when using the TOTO self-cleaning coating with surfactant. The        return pipe was extended below the coating surface inside the        pump reservoir. A small coil was produced, identified as        LRB776-8, using part A of the TOTO coating only (i.e., no        surfactant). A urethane applicator roll was used to coat this        coil.

Line Conditions/Run Details

-   -   Line Speed of 150 FPM (11.2 second oven dwell time)        -   i. Applicator roll at 50% over line speed        -   ii. Pick-up roll at 40% under line speed        -   iii. Oven Temperature: 250° F. (high and low)        -   iv. Coating: Toto THPC090402WC        -   v. Reducing Solvent: None        -   vi. Application Viscosity: No adjustment required; run as            received, water thin at about 71° F.        -   vii. Roll Types:            -   1. Top side applicator, ceramic, 11.0 inch diameter            -   2. Top side applicator, urethane 65 durometer, 11.0 inch                diameter            -   3. Top side pickup roll, chrome plated, 150 Ra, 6.0 inch                diameter            -   4. Roll Direction Reverse roll coated against sheet                tension        -   viii. Roll Speeds: Various—See FIG. 12        -   ix. Substrate:            -   1. LRB 776 trials 1-8 AAP's kynar white surface, 0.020″,                pre-coated with PPG's UC108219

Product observations

-   -   LRB 776—No. 1:        -   i. Toto THPC090402WC-A, part A only, two hard rolls (Trials            1-2)            -   1. Good coating flow (slight crows feet appearance)            -   2. Coating viscosity was stable in the pan            -   3. Coating was easy to clean up with water followed by a                MEK wipe            -   4. Uniform gloss            -   5. No foaming in the pump reservoir            -   6. Uneven coating thickness            -   7. No ability to squeeze out roll imperfections    -   LRB 776—No. 2:        -   i. Toto THPC090402WC-A, two hard rolls (Trials 3-5);            -   1. Added various amounts of TOTO part B to 4 gallons of                TOTO part A            -   2. No coating uniformity improvement was observed.    -   LRB 776—No. 3:        -   i. Toto THPC090402WC-A, part A only, urethane applicator            roll (Trials 6-8)            -   1. Even coating thickness            -   2. Good coating flow (slight crows feet appearance)            -   3. Coating easily wet the pre-coated sheet            -   4. Uniform gloss            -   5. No foaming in the pump reservoir

While various embodiments of the present disclosure have been describedin detail, it is apparent that modifications and adaptations of thoseembodiments will occur to those skilled in the art. However, it is to beexpressly understood that such modifications and adaptations are withinthe spirit and scope of the present disclosure.

1. A method comprising: (a) first producing a colored aluminum sheetproduct having a predetermined color and a predetermined gloss, thefirst producing step comprising: (i) roll coating a colored coating ontoan aluminum alloy sheet; and (ii) converting the colored coating into acolored layer, wherein the colored layer is located on an outer surfaceof the aluminum alloy sheet; (b) second producing an intermediatealuminum sheet product, the second producing step comprising: (i) rollcoating a barrier coating onto at least a portion of the colored layerof the colored aluminum sheet product; and (ii) converting the barriercoating into a barrier layer, wherein, after the converting step, thebarrier layer is located on at least a portion of the colored layer;wherein, after the second converting step, the intermediate aluminumsheet product retains the predetermined color and retains thepredetermined gloss of the colored aluminum sheet product; and (c) thirdproducing a colored self-cleaning aluminum sheet product, the thirdproducing comprising: (i) roll coating a self-cleaning coating onto atleast a portion of the barrier layer of the intermediate aluminum sheetproduct; and (ii) converting the self-cleaning coating into aself-cleaning layer, wherein, after the converting step, theself-cleaning layer is on at least a portion of the barrier layer;wherein, the colored self-cleaning aluminum sheet product retains thepredetermined color and retains the predetermined gloss of the coloredaluminum sheet product.
 2. The method of claim 1, wherein the secondproducing and the third producing steps are completed in sequence and ina single roll coating unit.
 3. The method of claim 1, wherein the firstproducing, the second producing and the third producing are completed insequence and in a single roll coating unit.
 4. The method of claim 1,wherein the barrier coating comprises silica.
 5. The method of claim 1,wherein the self-cleaning coating is surfactant-free.
 6. The method ofclaim 1, wherein the self-cleaning coating comprises titanium dioxide.7. The method of claim 1, wherein the colored self-cleaning aluminumsheet product has a Delta E that is not greater than about 10 ascompared to the colored aluminum sheet product.
 8. The method of claim1, wherein the colored self-cleaning aluminum sheet product has aDelta-E that is not greater than about 5 as compared to the coloredaluminum sheet product.
 9. The method of claim 1, wherein the coloredself-cleaning aluminum sheet product has a Delta-E that is not greaterthan about 1 as compared to the colored aluminum sheet product.
 10. Themethod of claim 1, wherein the colored self-cleaning aluminum sheetproduct has a gloss that is not greater than about 20 units differentthan the gloss of the colored aluminum sheet product.
 11. The method ofclaim 1, wherein the colored self-cleaning aluminum sheet product has agloss that is not greater than about 10 units than the gloss of thecolored aluminum sheet product.
 12. The method of claim 1, wherein thecolored self-cleaning aluminum sheet product has a gloss that is notgreater than about 5 units different than the gloss of the coloredaluminum sheet product.
 13. The method of claim 1, wherein the coloredself-cleaning aluminum sheet product has a gloss that is not greaterthan about 1 unit different than the gloss of the colored aluminum sheetproduct.
 14. The method of claim 1, wherein the colored self-cleaningaluminum sheet product realizes a uniformity rating of at least about D.15. The method of claim 1, wherein the colored self-cleaning aluminumsheet product realizes a uniformity rating of at least about B.
 16. Themethod of claim 1, wherein the colored self-cleaning aluminum sheetproduct realizes a uniformity rating of at least about A.
 17. The methodof claim 1, wherein the colored self-cleaning aluminum sheet product isiridescent-free.
 18. The method of claim 1, wherein the barrier layerhas a thickness of not greater than about 1 micron.
 19. The method ofclaim 1, wherein the self-cleaning layer has a thickness of not greaterthan about 1 micron.
 20. The method of claim 1, wherein theself-cleaning layer achieves a water contact angle of not greater thanabout 25°.